Many current day polymeric systems utilize RAP as a fire retardant additive. In some of the current day systems, particulate RAP is added to the polymeric system during the processing stage. Utilized in this manner, RAP has been an effective flame retardant for many thermoplastics and operates in both the vapor and condensed phases. For example, U.S. Pat. Nos. 4,105,735; 4,187,207; and 4,670,487.
In other systems, RAP is encapsulated in another polymer before introduction to the host polymer in hopes of reducing the emission of phosphorus gases. For example, U.S. Pat. No. 4,208,317 discloses encapsulating RAP in various polymers, none of which have the highly successful liquid crystalline structure of the liquid crystal polymer utilized in this invention. Other examples of RAP encapsulation are shown in U.S. Pat. Nos. 4,440,880 and 4,471,080, none of which have successfully decreased the phosphine emissions to acceptable, non-toxic levels.
While the benefits of RAP as a fire retardant additive in plastics are many as shown by the previously cited patents, RAPs' potential use is seriously compromised by its propensity to undergo hydrolysis followed by emission of the highly toxic gas phosphine (PH.sub.3). This emission of phosphine from materials comprised of a RAP containing polymer has far-reaching implications in terms of the future commercialization of any plastic product containing RAP. For example, many fire retardant products containing RAP are used in confined enclosures with limited ventilation, such as modern energy efficient buildings. The limited ventilation leads to accumulation of toxic levels of phosphine emitted from the enclosures.
To date, no RAP containing fire retardant plastic formulations or technologies exist which yield acceptable, non-toxic phosphine emission levels. Consequently, a need exists for a plastic formulation and technology that is capable of reducing phosphine emissions from RAP containing formulations to non-toxic levels while maintaining the fire retardant benefits.